This invention relates to an absorbent article in which superabsorbent material is contained in discrete pockets on a selectively stretchable substrate. The pockets may be present in one or more layers. When the superabsorbent material becomes wet, the resulting expansion causes adjacent pockets to engage and press against each other. The selectively stretchable substrate permits the expanding pockets to push each other apart in a selected direction. Furthermore, when the absorbent layer is stretched in the selected direction the pockets are increasingly separated from each other.
Absorbent composites suitable for use in disposable absorbent garments such as diapers, adult incontinent products, and the like, are known. Such absorbent composites are described, for example, in U.S. Pat. No. 4,699,619 issued Oct. 13, 1987 to Bemardin, U.S. Pat. No. 4,798,603 issued Jan. 17, 1989 to Meyer et al., U.S. Pat. No. 4,834,735 issued May 30, 1989 to Alemany et al., U.S. Pat. No. 5,147,343 issued Sep. 15, 1992 to Kellenberger, and U.S. Pat. No. 5,149,335 issued Sep. 22, 1992, to Kellenberger et al.
Generally, such absorbent composites comprise a matrix for containing a high-absorbency material. Suitable matrices for containing the high-absorbency material include fibrous matrixes, such as those formed from air-laid cellulosic fibers or a coform material comprising cellulosic fibers and meltblown polyolefin fibers. A wide variety of high absorbency materials (also known as superabsorbent materials) are known to those skilled in the art. See, for example, U.S. Pat. No. 4,076,663 issued Feb. 28, 1978 to Masuda et al, U.S. Pat. No. 4,286,082 issued Aug. 25, 1981 to Tsubakimoto et al., U.S. Pat. No. 4,062,817 issued Dec. 13, 1977 to Westerman, and U.S. Pat. No. 4,340,706 issued Jul. 20, 1982 to Obayashi et al.
Many known absorbent composites comprising a high-absorbency material employ the high-absorbency material in relatively low concentrations. That is, many of the absorbent composites comprise air-laid cellulosic fibers and less than about 20 weight percent of high-absorbency material. This is due to several factors.
Many high-absorbency materials are unable to absorb a liquid at the rate at which the liquid is applied to the absorbent composites during use. Accordingly, a relatively high concentration of fibrous material is desirable to temporarily hold the liquid until the high-absorbency material can absorb it. Further, the fibers serve to separate the particles of high-absorbency material so that gel-blocking does not occur. Gel-blocking refers to the situation wherein particles of high-absorbency material deform during swelling and block the interstitial spaces between the particles, or between the particles and fibers, thus preventing the flow of liquid through the interstitial spaces.
The presence of a relatively low concentration of high-absorbency material and a relatively greater concentration of fibrous materials has resulted in the production of absorbent composites which tend to be relatively thick. In some instances, the use of a relatively thick absorbent composite in a disposable absorbent garment is acceptable. However, in recent years it has become increasingly desirable to produce absorbent composites which are thin compared to the more traditional absorbent composites but which still possess the same absorbent capacity. The desire to produce relatively thin absorbent composites has resulted in the desire to incorporate ever-increasing amounts of high-absorbency material into the absorbent composites. This is because the absorbent capacity of such high-absorbency materials is generally many times greater than the absorbent capacity of fibrous materials. For example, a fibrous matrix of wood pulp fluff can absorb about 7-9 grams of a liquid, (such as 0.9 weight percent saline) per gram of wood pulp fluff, while the high-absorbency materials can absorb at least about 15, preferably at least about 20, and often at least about 25 grams of liquid, such as 0.9 weight percent saline, per gram of the high-absorbency material.
A trend toward more stretchable diapers is illustrated in U.S. Pat. No. 5,846,232 issued to Serbiak et al., and in U.S. Pat. No. 5,451,219 issued to Suzuki et al. These references disclose various elastic or extensible structures in the diapers to achieve stretchability.
U.S. Pat. No. 5,601,542, issued to Melius et al., discloses an absorbent article in which superabsorbent material is contained in layers of discrete pouches. The pouches are adjacent one another, and are formed in one or more substrate layers. When the superabsorbent material becomes wet, the substrates either do not stretch or stretch uncontrollably in all directions. In the former case, the absorbent capacity of the superabsorbent may be inhibited because of the externally applied pressure of the substrates working against the swelling pressure of the superabsorbent. In the latter case, the uncontrolled stretching of the substrate can cause the wet superabsorbent gel to shift, reducing the effectiveness of the absorbent system, and causing discomfort to the wearer.
The present invention is an absorbent article having at least one absorbent composite which is selectively stretchable in one direction, wherein superabsorbent material is present in discrete pockets or pouches in or on a selectively stretchable substrate. The absorbent article includes at least a substantially liquid impermeable, vapor permeable back sheet, a liquid permeable top sheet positioned in facing relation with the back sheet, and one or more of the selectively stretchable absorbent layers between the top sheet and the back sheet.
The substrate in the absorbent composite is selectively stretchable in one direction. For instance, the substrate in a diaper product may be laterally stretchable between the legs of the wearer, without being longitudinally stretchable between the waist regions of the wearer. In one embodiment, the substrate may be a neck-bonded laminate of a necked, inelastic nonwoven filament web to an elastic film. Neck-bonded laminates of this type are described in U.S. Pat. No. 5,883,028, issued to Morman et al., the disclosure of which is incorporated by reference. Other suitable substrates include without limitation necked spunbond webs and necked, creped spunbond webs.
In one embodiment, the selectively stretchable substrate may comprise two layers of material which are joined together to form a plurality of pockets between them. The pockets may be formed in one or both layers. At least one of the layers should be water-pervious. The other layer may be water-pervious or water-impervious. The absorbent composite may also contain two of the selectively stretchable substrates, joined together with a plurality of pockets between them. In either case, the superabsorbent material is located in the pockets.
During use of the absorbent article, the pockets maintain the desired distribution of the superabsorbent material in the absorbent composite. The selectively stretchable substrate permits stretching of the absorbent layer in a desired direction, to accommodate movement of the wearer as well as swelling of the superabsorbent when wet. The absorbent composite can be used in a wide variety of absorbent articles including, for instance, personal care absorbent products and medical absorbent products. Personal care absorbent products include diapers, training pants, swim wear, absorbent underpants, baby wipes, adult incontinence garments and feminine hygiene products. Medical absorbent products include absorbent garments, underpads, bandages, absorbent drapes, and medical wipes.
With the foregoing in mind, it is a feature and advantage of the invention to provide an absorbent article which has a relatively stretchable absorbent composite and a distribution of pockets containing superabsorbent material, to alleviate gel blocking.
It is also a feature and advantage of the invention to provide an absorbent article having a selectively stretchable absorbent composite which preferentially stretches in a desired direction.
The foregoing and other features and advantages will become further apparent from the following detailed description of the presently preferred embodiments. The detailed description is illustrative rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.